1. Field of the Invention
The present invention relates to a surface-position detection device and a scanning projection exposure apparatus using the device. More particularly, the invention precisely and easily adjusts each exposure region of a semiconductor wafer (substrate) mounted on a wafer stage to a focal plane of a projection lens system (projection optical system) in a step-and-repeat or step-and-scan projection exposure apparatus for manufacturing semiconductor devices.
2. Description of the Related Art
At present, circuit patterns are becoming finer as the degree of integration of super LSIs (large-scale integrated circuits) increases, so that projection lens systems used in respective projection exposure apparatuses tend to have larger NAs (numerical apertures). As a result, allowable focal depths of respective lens systems in a circuit-pattern transfer process are becoming smaller. In addition, the sizes of areas to be exposed by projection lens systems are becoming larger.
Accordingly, in order to realize excellent transfer of a circuit pattern over the entire large-size region to be exposed, it is necessary to accurately position the entire region (shot) to be exposed of a wafer within the allowable focal depth of the projection lens system.
For that purpose, it is important to precisely detect the position and inclination of the surface of a wafer with respect to the focal plane, i.e., the plane where the image of a circuit, pattern on a reticle is focused, of a projection lens system, and adjust the position and inclination of the surface of the wafer.
Recently, there is an increasing demand for a scanning projection exposure apparatus which can increase an exposure region and an NA while using a projection lens equivalent to that used in a stepper.
In such a scanning exposure apparatus, in order to realize excellent transfer of a circuit pattern of a reticle over the entire region to be exposed, the position and inclination of the surface of a wafer, on which the circuit pattern is to be transferred, with respect to the image of the circuit pattern (the focal plane of the projection optical system) are precisely detected in synchronization with a scanning operation, and the surface of the wafer is sequentially adjusted to the optimum imaging surface of the projection optical system by continuously performing correction driving of auto-focus/auto-leveling during scanning exposure.
For example, a method using a detection optical system in which a light beam is projected from an oblique direction onto the surface of a wafer, and deviation in a reflection point of reflected light from the surface of the wafer is detected as deviation of reflected light on a sensor, and a method in which a plurality of positions on the surface of the wafer are detected using a gap sensor, such as an air microsensor, an electrostatic capacity sensor, or the like, and the surface position of the wafer is obtained based on the result of the detection are known as methods for detecting the height and the position of the surface of the wafer in the above-described exposure apparatus.
In a surface-position detection method in a scanning projection exposure apparatus in which the height of a wafer is continuously detected by performing relative scanning, in consideration of ease of control, positions to be measured are arranged, taking a point of start of exposure as a reference point, by (1) obtaining the minimum control frequency in the entire surface-position detection system from (a) the detection region of a measuring sensor, (b) a sampling period corresponding to the synchronizing scanning speed during exposure and the residual vibration mode of the structure of the apparatus, and (c) the control frequency of a control system, and (2) setting a constant sampling period based on the minimum control frequency.
In actual production facilities, however, chips having various sizes are produced using shrinked plates, cut-down plates, and the like, because various finer chips are demanded. Hence, in the above-described arrangement of sampling points to be measured depending on the control system, surface-position information is uncertain at peripheral portions, particularly at a portion near the position of an end of exposure by an amount within a fixed sampling interval, resulting in the generation of local defocus.
It is an object of the present invention to provide a surface-position detection device which can precisely adjust a wafer or a photosensitive substrate to a focal plane of a projection optical system even when the size of a shot changes, a projection exposure apparatus using the device, and a device manufacturing method using the apparatus.
According to one aspect of the present invention, a surface-position detection device for detecting surface-position information of a photosensitive plate disposed near an imaging surface of a projection optical system when performing projection exposure of a pattern on a surface of an object onto the photosensitive substrate via the projection optical system by performing relative scanning between the photosensitive substrate and the object includes detection means for detecting the surface-position information within a shot region of the photosensitive substrate in a direction of an optical axis of the projection optical system, and means for causing the detection means to detect the surface-position information at a plurality of points arranged so that a first end of the plurality of points coincides with a position to start a scanning exposure and a second end of the plurality of points coincides with a position to end the scanning exposure in accordance with a size of the shot region.
In one embodiment, an interval between adjacent points of the plurality of points is variable in accordance with a length of the scanning exposure in each shot region of the photosensitive substrate.
In another embodiment, the plurality of points are arranged with a substantially equal interval making the position to start a scanning exposure substantially equivalent to the first end and the position to end the scanning exposure substantially equivalent to the second end.
In still another embodiment, the size of the shot region is individually obtained in advance for each shot region from layout information of a region to be exposed on the photosensitive substrate.
According to another aspect of the present invention, a surface-position detection device for detecting surface-position information of a wafer when performing projection exposure of a pattern on a surface of a reticle onto the wafer via a projection optical system by performing relative scanning between the wafer and the reticle includes detection means for continuously detecting the surface-position information within a shot region of the wafer in a direction of an optical axis of the projection optical system, and means for causing the detection means to detect the surface-position information at a plurality of points arranged so that a first end of the plurality of points coincides with a position to start a scanning exposure and a second end of the plurality of points coincides with a position to end the scanning exposure in accordance with a size of the shot region.
In one embodiment, the surface-position information comprises inclination of the wafer with respect to a plane perpendicular to the direction of the optical axis of the projection optical axis.
In another embodiment, an interval between adjacent points of the plurality of points is variable in accordance with a length of the scanning exposure in each shot region within the wafer.
In still another embodiment, the plurality of points are arranged with a substantially equal interval making the position to start a scanning exposure substantially equivalent to the first end and the position to end the scanning exposure substantially equivalent to the second end.
In yet another embodiment, the size of the shot region is individually obtained in advance for each shot region from layout information of a region to be exposed on the wafer.
According to still another aspect of the present invention, a scanning projection exposure apparatus for performing projection exposure of a pattern on a surface of an object onto a shot region on a surface of a photosensitive substrate mounted on a movable stage by a projection optical system while causing scanning means to perform scanning between the object and the movable stage by causing the object and the movable stage to be synchronized with a velocity ratio corresponding to a photographing magnification of the projection optical system includes detection means for detecting surface-position information within a shot region of the photosensitive substrate in a direction of an optical axis of the projection optical system, and means for causing the detection means to detect the surface-position information at a plurality of points arranged so that a first end of the plurality of points coincides with a position to start a scanning exposure and a second end of the plurality of points coincides with a position to end the scanning exposure in accordance with a size of the shot region.
In one embodiment, an interval between adjacent points of the plurality of points is variable in accordance with a length of the scanning exposure in each shot region of the photosensitive substrate.
In another embodiment, the plurality of points are arranged with a substantially equal interval making the position to start a scanning exposure substantially equivalent to the first end and the position to end the scanning exposure substantially equivalent to the second end.
In still another embodiment, the size of the shot region is individually obtained in advance for each shot region from layout information of a region to be exposed on the photosensitive substrate.
In yet another embodiment, a position of the shot region being subjected to projection exposure in the direction of the optical axis is corrected based on the surface-position information.
In yet a further embodiment, in the correction of the position of the shot region in the direction of the optical axis, a target position for correction based on a result of detection at each of the plurality of points changes in a scanning direction depending on a position of each of the plurality of points.
According to yet another aspect of the present invention, a position detection device for detecting position information of a photosensitive substrate when performing projection exposure of a pattern on a surface of an object onto the photosensitive substrate via a projection optical system by scanning the pattern includes detection means for detecting the position information within a shot region of the photosensitive substrate in the projection optical system, and means for causing the detection means to detect the position information at a plurality of points arranged so that a first end of the plurality of points coincides with a position to start a scanning exposure and a second end of the plurality of points coincides with a position to end the scanning exposure in accordance with a size of the shot region.
In one embodiment, the position information comprises a position in a direction of an optical axis of the projection optical system.
In another embodiment, the position information comprises alignment error of the photosensitive substrate with respect to the object.
In still another embodiment, each of the plurality of points comprises a position where an alignment mark is formed on the photosensitive substrate.
According to yet a further aspect of the present invention, a position detection device for detecting position information of a photosensitive substrate, when performing projection exposure of a pattern on a surface of an object onto the photosensitive substrate via a projection optical system by scanning the pattern, includes a projection optical system for projecting light onto the photosensitive substrate, a receiving optical system for receiving light from the photosensitive substrate, and a stage for mounting the photosensitive substrate. A relationship between a movement of the stage and a detection position determined by the projection optical system and the receiving optical system is provided so as to be able to detect the position information at a plurality of points whose first end coincides with a position to start a scanning exposure and whose second end coincides with a position to end the scanning exposure on the photosensitive substrate.
According to still another aspect of the present invention, a wafer whose surface is subjected to projection exposure via a projection optical system by scanning a pattern on a surface of a reticle includes a plurality of alignment marks whose first end is arranged to coincide with a position to start a scanning exposure and whose second end is arranged to coincide with a position to end the scanning exposure in accordance with a size of each shot region.
According to still another aspect of the present invention, a device manufacturing method for manufacturing devices by performing projection exposure of a pattern on a surface of an object onto a photosensitive substrate via a projection optical system by scanning the pattern followed by a developing process includes the steps of detecting surface-position information at a plurality of points whose first end is arranged to coincide with a position to start the scanning exposure and whose second end is arranged to coincide with a position to start the scanning exposure in accordance with a size of a shot region within the photosensitive substrate, positioning the photosensitive substrate using the surface-position information, and exposing the photosensitive substrate which provides devices.
In one embodiment, an interval between adjacent points of the plurality of points is variable in accordance with a length of the scanning exposure in each shot region of the photosensitive substrate.
In another embodiment, the plurality of points are arranged with a substantially equal interval making the position to start the scanning exposure substantially equivalent to the first end and the position to end the scanning exposure substantially equivalent to the second end.
In still another embodiment, a size of the shot region s individually obtained in advance for each shot region from layout information of a region to be exposed on the photosensitive substrate.
In yet another embodiment, a position of the shot region being subjected to projection exposure in the direction of an optical axis of the projection optical system is corrected based on the surface-position information.
In yet a further embodiment, in the correction of the position of the shot region in the direction of the optical axis, a target position for correction based on a result of detection at each of the plurality of points changes in a scanning direction depending on a position of each of the plurality of points.
According to still another aspect of the present invention, a device manufacturing method for manufacturing devices by performing projection exposure of a pattern on a surface of a reticle onto a wafer, via a projection optical system by scanning the pattern followed by a developing process includes the steps of detecting surface-position information at a plurality of points whose first end is arranged to coincide with a position to start the scanning exposure and whose second end is arranged to coincide with a position to end the scanning exposure in accordance with a size of a shot region within the photosensitive substrate, positioning the photosensitive substrate using the surface-position information, and exposing the wafer which provides devices.
In one embodiment, an interval between adjacent points of the plurality of points is variable in accordance with a length of the scanning exposure in each shot region of the photosensitive substrate.
In another embodiment, the plurality of points are arranged with a substantially equal interval making the position to start the scanning exposure substantilly equivalent to the first end and the position to end the scanning exposure substantially equivalent to the second end.
In still another embodiment, a size of the shot region is individually obtained in advance for each shot region from layout information of a region to be exposed on the photosensitive substrate.
According to still another aspect of the present invention, a device manufacturing method for manufacturing devices by performing projection exposure of a pattern on a surface of an object onto a photosensitive substrate via a projection optical system by scanning the pattern followed by a developing process includes the steps of detecting position information at a plurality of points whose first end is arranged to coincide with a position to start the scanning exposure and whose second end is arranged to coincide with a position to end the scanning exposure in accordance with a size of a shot region within the photosensitive substrate, positioning the photosensitive substrate using the position information, and exposing the photosensitive substrate which provides devices.
In one embodiment, the position information comprises a position in a direction of an optical axis of the projection optical system.
In another embodiment, the position information comprises alignment error of the photosensitive substrate with respect to the surface of the object.
In still another embodiment, each of the plurality of points comprises a position where an alignment mark is formed on the photosensitive substrate.
The foregoing and other objects, advantages, and features of the present invention will become more apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.